Vehicle window and method of making the same

ABSTRACT

A vehicle window comprising a relatively thin sheet of clear plastic material having opposed surfaces, an electrically operable defrosting grid adhered to one surface of the relatively thin sheet, and a relatively thick substrate layer of clear plastic material having opposed surfaces curved into a vehicle window configuration. The relatively thick substrate layer is adhered to the one surface of the relatively thin sheet and the electrically operable defrosting grid adhered thereto while in contact therewith in a molten state under heat and pressure within a cavity defined by two generally parallel curved die surfaces of cooperating injection molding dies so that upon solidification the surfaces of the relatively thin sheet are retained in a curved configuration in generally parallel coextensive relation to corresponding curved surfaces of the relatively thick substrate layer and a method of making the window wherein the electrically operable defrosting grid is formed by silk screening onto one surface of the relatively thin sheet while in a substantially planar condition a curable electrically conductive ink in the form of a defrosting grid and then curing the curable electrically conductive ink on the one surface of said relatively thin sheet so that the defrosting grid is stably adhered thereto.

This invention relates to windows and more particularly to windowshaving electrical defrosting grids embodied therein such as the rearwindows of motor vehicles.

Motor vehicle designs particularly for passenger vehicles require agreat latitude in the curvatures which are considered desirable from adesign standpoint and often such curvatures are desired in the windowsprovided. Recent designs have more and more gone to the round look atthe front and rear ends of the car. Particularly, in rear windows wheredefrosting is of great importance, the curvatures desired are becominggreater and greater. A cost problem in producing severely curved rearwindows is in embodying the electrical resistance heating elements inthe final product because heretofore it has not been possible to utilizethe more cost effective silk screening methods to provide the heatingelements because of the necessity to silk screen onto an essentiallyflat surface.

It is well known that glass has been the material of choice in motorvehicle rear windows for many years. It is also well known that plasticmaterials, such as polycarbonates, if employed in lieu of glass, couldreduce the weight of the rear window. Nevertheless, glass continues tobe used. It is apparent that, in order for motor vehicle makers to shiftfrom glass to plastics, the plastic window must be cost effective inother ways besides weight reduction.

One way in which additional cost effectiveness can be achieved relatesto the way the electrical defrosting system is embodied in the windowconstruction. For example, it would be desirably effective to have theelectrical grid quite close to the exterior surface but still protectedby being mounted inwardly of the exterior surface. With an arrangementof this type, the electrical grid can be made to effectively operatewith less power requirement with the resultant advantages in thecharacteristics and amount of conductive material needed to provide thesystem.

It is an object of the present invention to provide a vehicle windowwhich meets the cost effectiveness requirements set forth above. Inaccordance with the principles of the present invention, this objectiveis achieved by providing a vehicle window which comprises thecombination of three components: one, a thin clear sheet; two, anelectrically operable defrosting grid; and three, a relatively thickclear substrate layer. The relatively thin clear sheet is of a plasticmaterial having opposed surfaces. The electrically operable defrostinggrid is adhered to one surface of the thin sheet. The relatively thickclear substrate layer is of a plastic material having opposed surfacescurved into a vehicle window configuration. The relatively thicksubstrate layer is adhered to the one surface of the relatively thinsheet and the electrically operable defrosting grid attached theretowhile in contact therewith in a molten state under heat and pressurewithin a cavity defined by two generally parallel curved die surfaces ofcooperating injection molding dies so that, upon solidification, thesurfaces of said relatively thin sheet are retained in a curvedconfiguration in generally parallel coextensive relation tocorresponding curved surfaces of said relatively thick substrate layer.

The provision of the thin clear sheet as a basic component of the windowenables the particularly cost effective silk screening process to beused in making the window because the relatively thin sheet can have thesilk screening of the grid performed while in a planar condition andthen subsequently curved during the injection molding of the relativelythick substrate layer. Accordingly, another object of the presentinvention is to provide a method of making a window which can havefairly severe curvatures in two planes sufficient to accommodate a widevariety of designs having an electrical defrosting system which isprovided by a conventional silk screening process. In accordance withthe principles of the present invention, this objective is achieved byproviding a method of forming a window which comprises providing arelatively thin sheet of clear plastic material having opposed surfacesand silk screening onto one surface of the relatively thin sheet whilein a substantially flat planar condition a curable electricallyconductive ink in the form of a defrosting grid. The curableelectrically conductive ink is cured on the one surface of therelatively thin sheet so that the defrosting grid is stably adheredthereto. The relatively thin sheet with the defrosting grid adhered toone surface thereof is mounted adjacent a curved die surface of amolding die arranged to be disposed in cooperating relation with asecond molding die having a similarly shaped curved die surface. Thefirst and second molding dies are disposed in cooperating relation so asto bring the two curved die surfaces into generally parallel relation toform a die cavity with a spacing between the two curved die surfacessubstantially greater than the thickness of the thin sheet. Finally, aclear plastic material is injection molded under heat and pressurewithin the die cavity between the two generally parallel curved diesurfaces so as to form a window having curved exterior surfacescomprising a curved relatively thin clear sheet having the electricallyconductive grid adhered to one surface thereof and a relatively thickersubstrate layer of clear plastic molded in adhered relation to therelatively thin clear sheet.

Another object of the present invention is the provision of a vehiclewindow which comprises a relatively thin sheet of clear plastic materialhaving opposed surfaces, an electrically operable defrosting gridadhered to one surface of the relatively thin sheet, and a relativelythick substrate layer of clear plastic material having opposed surfacescurved into a vehicle window configuration. The relatively thicksubstrate layer is adhered to one surface of the relatively thin sheetand the electrically operable defrosting grid adhered thereto while incontact therewith in a molten state under heat and pressure within acavity of an injection molding device so that upon solidification thesurfaces of the relatively thin sheet are retained in a curvedconfiguration in generally parallel coextensive relation tocorresponding curved surfaces of the relatively thick substrate layer.

These and other objects of the present invention will become moreapparent during the course of the following detailed description andappended claims.

The invention may best be understood with reference to the accompanyingdrawings wherein an illustrative embodiment is shown.

IN THE DRAWINGS

FIG. 1 is a perspective view of a vehicle rear window constructed inaccordance with the principles of the present invention;

FIG. 2 is a generally schematic view illustrating a step in the processof making the window shown in FIG. 1;

FIG. 3 is a view similar to FIG. 2 illustrating a further step in themethod; and

FIG. 4 is a view similar to FIG. 2 showing a still further step in themethod of making the window of FIG. 1.

Referring now more particularly to the drawings, there is shown in FIG.1 a vehicle window, generally indicated at 10, which embodies theprinciples of the present invention. The window consists essentially ofthree components: a relatively thin sheet of clear plastic material 12,an electrically operable defrosting grid, generally indicated at 14, anda relatively thick substrate layer of clear plastic material 16.

The relatively thin sheet 12 is formed from any suitable thermoplasticmaterial. Preferred materials are taken from the group consisting ofpolycarbonate or polyester resin, with polycarbonate being a preferredembodiment. The relatively thin sheet 12 may be formed by anyappropriate method, such as extrusion or molding. The relatively thinsheet 12 has a thickness within an operative range of 5 to 40 mils and apreferred range of 10 to 30 mils. A preferred thickness for therelatively thin sheet 12 is approximately 20 mils.

The electrically operable defrosting grid 14 is of conventional formincluding a series of parallel wire-like elements 18 and a pair of bussbars 20 at opposite ends thereof. In the broadest aspects of the presentinvention, grid 14 may be formed in any suitable manner from anysuitable conductive material. However, in a preferred embodiment, thedefrosting grid 14 is formed by a conductive material in the form of anink applied to one surface of the thin sheet 12 through a silk screen.The ink is subsequently cured by heat. It will be understood, however,that the ink may be an ink which is capable of being cured by exposureto ultraviolet light or other means. A preferred example is epoxymaterial loaded with silver particles which is cured by heat inaccordance with conventional practice.

It will also be understood that the silk screening process which isutilized for applying the electrically operable defrosting grid 14 toone surface of the thin sheet 12 can also be utilized to provide thethin sheet with a border of black material provided by loading the epoxymaterial with carbon particles rather than the silver particles, all inaccordance with conventional silk screening practice.

It is also possible to provide the surface of the thin sheet 12 opposedto the surface which receives the electrically operable defrosting grid16 with an abrasive resistant coating. The coating is applied before thesilk screening process and preferably by a dipping procedure. Thispreferred procedure has the effect of coating both surfaces of therelatively thin sheet 12. Where the one surface which is to receive thesilk screening material is provided with an abrasive resistant coating,the coating serves to enable the silk screening inks to adhere moretenaciously thereto. The abrasive resistant coating preferably comprisesa thermoset material taken from the group consisting of polysiloxane,acrylic resin or aliphatic polyurethane.

The relatively thick substrate layer 16 is preferably formed fromthermoplastic material taken from the group consisting of polycarbonate,cyclic polyolefin and polymethyl methacrylate. The relatively thicksubstrate layer has a thickness within an operative range of 50 to 500mils and a preferred range of from 100 to 150 mils. A preferred exampleof the thickness of the relatively thick substrate layer isapproximately 125 mils.

FIG. 2 illustrates the preferred method of applying the electricallyoperable defrosting grid 14 to one surface of the relatively thin sheet12. As shown, the relatively thin sheet 12 is mounted on a support 22having a flat planar support surface 24. The thin sheet 12 is mounted onthe flat surface 24 so as to be supported in a planar condition duringthe silk screening process. The silk screening itself is of aconventional nature and includes a silk screen assembly, generallyindicated at 26, which includes a peripheral frame 28 and a silk screen30 having openings formed therein which define the parallel wireelements 18 and buss bars 20 of the electrically operable defrostinggrid 14. The silk screen 30 is loaded with an ink comprising an epoxyplastic material capable of being cured which is loaded withelectrically conductive particles, such as silver particles. After theink has been applied to the silk screen 30, a squeegee device 32 ismoved over the silk screen so as to pass the ink on the silk screenthrough the openings thereof and deposit the same on the upper surfaceof the thin sheet 12. After both the wire elements 18 and buss bars 20of the grid 14 have been applied to the surface of the relatively thinsheet 12, the applied ink is then cured in accordance with conventionalpractice by heating the same.

As previously indicated, the exterior of the relatively thin sheet 12can also be silk screened to provide a black marginal edge also inaccordance with conventional practice. This silk screening would beaccomplished with the use of a different ink where the silver particlesare replaced by carbon particles or the like.

It will be understood that while FIG. 2 illustrates the silk screeningprocess to be accomplished while the thin sheet 12 is in a planarcondition which is flat, it is within the contemplation of the presentinvention in the broadest aspects thereof to accomplish the silkscreening procedure on a continuous web in which case the planar surfacewould be cylindrical.

After the electrically operable defrosting grid has been applied andcured to the one surface of the thin sheet 12, the thin sheet 12 is thenmounted within a molding die, such as shown at 32 in FIG. 3. The moldingdie 32 includes a curved die surface 34 and the thin sheet 12 is mountedwith respect to the molding die 32 so that it is adjacent to the curvedsurface 34. As shown in FIG. 3, the curved surface may have curvature intwo planes which is a prevalent practice with respect to motor vehicletype rear windows.

It is contemplated that the relatively thin sheet 12 has a thicknesswhich when mounted in the molding die 32, would simply conform generallyto the curved die surface 34. Preferably, the relatively thin sheet 12is mounted within the molding die 32, adjacent the die surface 32 sothat a marginal edge extends beyond the die's moulding surface 34. Theoutwardly extending marginal edge portion has its upper surface engagedby a cooperating marginal edge of a second molding die 36 whichcooperates with the molding die 32 when moved into cooperating relationwith the die 32.

As best shown in FIG. 4, the cooperating molding die 36 includes acurved die surface 38 which is generally parallel with the curved diesurface 34 of the molding die 32. The curved die surfaces 34 and 38 forma die cavity when the molding dies 32 and 36 are moved into cooperatingrelation. The die cavity has a thickness between the curved die surfaces34 and 38 which is substantially greater than the thickness of therelatively thin sheet 12.

After the die members 32 and 36 have been moved into cooperatingrelation, the plastic material which is to form the substrate layer 16is introduced into the die cavity above the marginally grip thin sheet12 and injection molded under heat and pressure in accordance withconventional practice. During the injection molding the opposite surfaceof the relatively thin sheet is forced against the die surface 34 if ithas not already been engaged therewith. If desired, the thin sheet 12can be preformed to engaged the die surface 34 just before being mountedtherein.

The resulting window 10 includes exterior surfaces which are curved toconform with the die surfaces 34 and 38. The electrically operabledefrosting grid 14 is captured between the relatively thick substratelayer 16 and the relatively thin sheet 12 which now has a curvaturecorresponding to that of the substrate layer 16, retained by theadherence of the relatively thin sheet 12 to the substrate layer 16.

It thus will be seen that the objects of this invention have been fullyand effectively accomplished. It will be realized, however, that theforegoing preferred specific embodiment has been shown and described forthe purpose of this invention and is subject to change without departurefrom such principles. Therefore, this invention includes allmodifications encompassed within the spirit and scope of the followingclaims.

What is claimed is:
 1. A vehicle window comprisinga relatively thin sheet of clear plastic material having opposed surfaces, an electrically operable defrosting grid formed from a curable conductive ink cured to one surface of said relatively thin sheet, and a relatively thick substrate layer of clear plastic material having opposed surfaces curved into a vehicle window configuration, said relatively thick substrate layer being adhered to said one surface of said relatively thin sheet and the electrically operable defrosting grid cured thereto while in contact therewith in a molten state under heat and pressure within a cavity defined by two generally parallel curved die surfaces of cooperating injection molding dies so that upon solidification the surfaces of said relatively thin sheet are retained in a curved configuration in generally parallel coextensive relation to corresponding curved surfaces of said relatively thick substrate layer.
 2. A vehicle window as defined in claim 1 wherein said electrically conductive defrosting grid is silk screened to the one surface of said relatively thin sheet by depositing an electrically conductive ink on said one surface through a silk screen while the one surface is in a planar condition, the deposited ink being thereafter cured to adhere it to said one surface.
 3. A vehicle window as defined in claim 2 wherein the surface of said relatively thin sheet opposed to said one surface has a coating of an abrasive resistant material thereon, said opposed surface constituting an exterior surface of said vehicle window.
 4. A vehicle window as defined in claim 3 wherein said abrasive resistant material is a thermoset material taken from the group consisting of polysiloxane, acrylic resin or aliphatic polyurethane.
 5. A vehicle window as defined in claim 2 wherein said relatively thin sheet has a thickness within a range of 5-40 mils.
 6. A vehicle window as defined in claim 2 wherein said relatively thin sheet has a thickness within a range of 10-30 mils.
 7. A vehicle window as defined in claim 2 wherein said relatively thin sheet has a thickness of approximately 20 mils.
 8. A vehicle window as defined in claim 2 wherein said relatively thin sheet is formed from a thermoplastic material taken from the group consisting of polycarbonate or polyester resin.
 9. A vehicle window as defined in claim 2 wherein said relatively thick substrate layer has a thickness within a range of 50-500 mils.
 10. A vehicle window as defined in claim 2 wherein said relatively thick substrate layer has a thickness within a range of 100-150 mils.
 11. A vehicle window as defined in claim 2 wherein said relatively thick substrate layer has a thickness of approximately 125 mils.
 12. A vehicle window as defined in claim 2 wherein said relatively thick substrate layer is formed of a thermoplastic material taken from the group consisting of polycarbonate or cyclic polyolefin or polymethylmethacrylate or any modification thereof. 